Recently, compact and light portable electronic devices, such as smart phones, notebook and tablet computers, and media players, have been actively developed and produced. Batteries are commonly used as an internal power source for such portable devices to enable the device to operate when external power sources are not available. Batteries may employ any of a number of electrochemical technologies and may be manufactured in a variety of form factors. For portable devices, interest in pouch type lithium ion polymer batteries (also referred to as lithium polymer batteries has increased because of low manufacturing costs, light weight, and easy modification in shape.
A pouch type lithium polymer battery is constructed by mounting an electrode assembly in a pouch type case that is made of a multi-layer laminate sheet. In conventional pouch type batteries, the multi-layer laminate sheet has a core layer that is a metallic foil. The metallic foil is substantially moisture and oxygen impervious, to prevent undesirable reactions from moisture or oxygen interacting with an electrolyte inside the case. When the case is sealed, the metal foil is exposed around the edges of the case and thus needs to be insulated to prevent corrosion of the pouch material, which may occur if the metallic foil is grounded or electrically biased as a result of unintended contact with other metal parts in the portable device. Typically, to insulate the metallic foil, the sealed edges of the case are manually folded against the sides of the case, and tape is then placed over the sealed edges to insulate the metallic foil and secure the edges against the sides of the case. This manual process of insulating the metallic foil can be time consuming and thus expensive. Furthermore, folding the sealed edges in this manner and applying tape over them increases the overall size of the battery. This may limit the size of the electrode assembly that can be placed inside the case; alternatively, it may reduce valuable space within the portable electronic device in which the battery is installed.